The core of a ski can be made in different ways, for example, by superimposing or juxtaposing a number of wooden elements in the form of layers assembled with one another, by assembling parts made of different materials, such as parts made of synthetic material, wooden parts, and resin-impregnated fabric, by machining an alveolar structure, such as an aluminum or paper honeycomb, or by injecting a foam made of a synthetic material.
All skis known heretofore can be equated with beams having relatively good elastic characteristics, or in other words capable of resuming their initial shapes after being deformed. However, depending on the materials used in the ski structure, the time required for the ski to return to the original shape can vary considerably. This type of feature defines the liveliness of a ski. The behavior of the ski is intimately linked to its ability to react to passing over bumps and hollows and in making turns.
Certain skis, especially skis whose core is made of injected synthetic material with a covering part simultaneously forming the upper and side surfaces of the ski, frequently exhibit a lack of liveliness which is disadvantageous for the behavior of the ski. In addition, the use of certain materials or the choice of certain shapes can also result in excess damping of the ski, conferring nondynamic behavior on the ski.
It is known from AT 388,875 to make a ski whose structure is composed of a plurality of layers between which elastic films are interposed. These films work in shear, permitting relative displacement of the various layers of the structure, thereby improving flexibility and especially the solidity of the ski.
Another significant characteristic of a ski is the ability to absorb vibrations generated by an impact of a sole of the ski with snow. These vibrations are microdeformations generated at high frequencies. A ski can be damped or resonant and its behavior, its ability to ski, and its comfort are linked to this.
Attempts have been made to trap the propagation of vibrations between the tip and the area of the ski on which a skier's foot is mounted by a barrier constituted by an damping element. Document FR 2,599,636 describes a ski of this type, in which the core is made of a hard material and therefore resonant. This arrangement is designed to limit the propagation of the vibrations described, by providing cells in the faces of the core and placement in these cells of a material that absorbs the vibrations.
Document FR 2,618,344 describes a device that is designed to prevent propagation of vibrational waves not only at the surface but also inside the core structure. This damping is obtained by providing plugs of an absorbent material in the median plane of the core.